DESCRIPTION: The goal of the proposed experiments is to elucidate the structure and function of phosphatidylinositol-phosphate kinases (PIPKs) in the nucleus. During the previous grant period, Dr. Anderson defined type I and II PIP5Ks, novel lipid kinases, which also produce PI3, 4P2 and PI3, 4,5, P2. Localization experiments demonstrated that PIPKs and PIP2 are co-localized in a distinctive pattern termed "nuclear speckle" within the nucleus and that these compounds participate in novel nuclear phosphoinositide signaling pathways. To test this hypothesis, the proposal has three specific aims. Aim 1 will identify the nuclear localization sequences within PIP5KII and determine whether nuclear localization of this kinase is regulated. In Aim 2, mutants of PIPKs will be generated, and their effect on nuclear signaling pathways will be determined. Additional experiments will focus on identifying and characterizing nuclear proteins that interact with PIPKs. Experiments proposed in Aim 3 will further characterize the nuclear compartment containing the PIPKs by biochemical and photochemical methods.